open a file without download dialog box

In my user screen I have view link, if I click this link it will go to servlet and open a document. It is opening properly, but while opening the attachment it generates one dialog box like file Open, Save or Cancel button, if I click open after that it is opening the document. But my query is it should not display this dialog box, once I click the link it should open the document automatically using HttpServletResponse. Can any one help me to avoid the pop up window?.All the documents were stored as Blob in the database. plz help me to resolve this issue